What are cleft sentences?

Cleft sentences are complex sentences that are used to emphasise one particular part of a sentence. They are particularly useful in writing where we cannot use intonation for emphasis, but they are also frequently used in speech.

Types of cleft sentences

The reason why, the thing that, the person/people who, the place where, the day when…

We can focus on an element of the sentence by using these structures with a relative clause. We use the relative pronouns in the same way we use them in any relative clause.

It + be + phrase + relative clause

Instead of the person who, the thing that, etc. we can also use an introductory it, the verb be in any verb tense that we may need, and the element that we want to focus on.

We can use who/which or that after a noun phrase, e.g. Sheila, the book, etc. But we should use that after adverbial phrases, e.g. under the mattress, on Monday, etc.

Note that we can also use whenafter noun phrases, but not after adverbial phrases. Compare:

It’s Monday when I have to call.

It’s on Monday that I have to call.

The thing/s that = What/All

We can also use what or all (more emphasis) instead of the thing/s that to focus on an element of the sentence.

What + subject + do/does/did/ + is/was + (to) infinitive

We use this structure when we want to focus on the verb or verb phrase. In these structures, we can use an infinitive with or without to.

What happens is (that) … / What happened was (that)

We use this structure when we want to focus on a whole sentence, and not only on an element in the sentence.